ryu_js/pretty/
mod.rs

1mod exponent;
2mod mantissa;
3
4use self::exponent::{write_exponent2, write_exponent3};
5use self::mantissa::{write_mantissa, write_mantissa_long};
6use crate::common;
7use crate::d2s::{self, d2d, DOUBLE_EXPONENT_BITS, DOUBLE_MANTISSA_BITS};
8use crate::f2s::{f2d, FLOAT_EXPONENT_BITS, FLOAT_MANTISSA_BITS};
9use core::ptr;
10#[cfg(feature = "no-panic")]
11use no_panic::no_panic;
12
13pub mod to_fixed;
14pub use to_fixed::format64_to_fixed;
15
16/// Print f64 to the given buffer and return number of bytes written.
17///
18/// At most 25 bytes will be written.
19///
20/// ## Special cases
21///
22/// This function **does not** check for NaN or infinity. If the input
23/// number is not a finite float, the printed representation will be some
24/// correctly formatted but unspecified numerical value.
25///
26/// Please check [`is_finite`] yourself before calling this function, or
27/// check [`is_nan`] and [`is_infinite`] and handle those cases yourself.
28///
29/// [`is_finite`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_finite
30/// [`is_nan`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_nan
31/// [`is_infinite`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_infinite
32///
33/// ## Safety
34///
35/// The `result` pointer argument must point to sufficiently many writable bytes
36/// to hold Ryū's representation of `f`.
37///
38/// ## Example
39///
40/// ```
41/// use std::{mem::MaybeUninit, slice, str};
42///
43/// let f = 1.234f64;
44///
45/// unsafe {
46///     let mut buffer = [MaybeUninit::<u8>::uninit(); 25];
47///     let len = ryu_js::raw::format64(f, buffer.as_mut_ptr() as *mut u8);
48///     let slice = slice::from_raw_parts(buffer.as_ptr() as *const u8, len);
49///     let print = str::from_utf8_unchecked(slice);
50///     assert_eq!(print, "1.234");
51/// }
52/// ```
53#[must_use]
54#[cfg_attr(feature = "no-panic", no_panic)]
55pub unsafe fn format64(f: f64, result: *mut u8) -> usize {
56    debug_assert!(!result.is_null());
57
58    let bits = f.to_bits();
59    let sign = ((bits >> (DOUBLE_MANTISSA_BITS + DOUBLE_EXPONENT_BITS)) & 1) != 0;
60    let ieee_mantissa = bits & ((1u64 << DOUBLE_MANTISSA_BITS) - 1);
61    let ieee_exponent =
62        (bits >> DOUBLE_MANTISSA_BITS) as u32 & ((1u32 << DOUBLE_EXPONENT_BITS) - 1);
63
64    if ieee_exponent == 0 && ieee_mantissa == 0 {
65        *result = b'0';
66        return 1;
67    }
68
69    let mut index = 0isize;
70    if sign {
71        *result = b'-';
72        index += 1;
73    }
74
75    let v = d2d(ieee_mantissa, ieee_exponent);
76
77    let length = d2s::decimal_length17(v.mantissa) as isize;
78    let k = v.exponent as isize;
79    let kk = length + k; // 10^(kk-1) <= v < 10^kk
80    debug_assert!(k >= -324);
81
82    if 0 <= k && kk <= 21 {
83        // 1234e7 -> 12340000000.0
84        write_mantissa_long(v.mantissa, result.offset(index + length));
85        for i in length..kk {
86            *result.offset(index + i) = b'0';
87        }
88        index as usize + kk as usize
89    } else if 0 < kk && kk <= 21 {
90        // 1234e-2 -> 12.34
91        write_mantissa_long(v.mantissa, result.offset(index + length + 1));
92        ptr::copy(result.offset(index + 1), result.offset(index), kk as usize);
93        *result.offset(index + kk) = b'.';
94        index as usize + length as usize + 1
95    } else if -6 < kk && kk <= 0 {
96        // 1234e-6 -> 0.001234
97        *result.offset(index) = b'0';
98        *result.offset(index + 1) = b'.';
99        let offset = 2 - kk;
100        for i in 2..offset {
101            *result.offset(index + i) = b'0';
102        }
103        write_mantissa_long(v.mantissa, result.offset(index + length + offset));
104        index as usize + length as usize + offset as usize
105    } else if length == 1 {
106        // 1e+30
107        *result.offset(index) = b'0' + v.mantissa as u8;
108        *result.offset(index + 1) = b'e';
109        index as usize + 2 + write_exponent3(kk - 1, result.offset(index + 2))
110    } else {
111        // 1234e30 -> 1.234e+33
112        write_mantissa_long(v.mantissa, result.offset(index + length + 1));
113        *result.offset(index) = *result.offset(index + 1);
114        *result.offset(index + 1) = b'.';
115        *result.offset(index + length + 1) = b'e';
116        index as usize
117            + length as usize
118            + 2
119            + write_exponent3(kk - 1, result.offset(index + length + 2))
120    }
121}
122
123/// Print f32 to the given buffer and return number of bytes written.
124///
125/// At most 22 bytes will be written.
126///
127/// ## Special cases
128///
129/// This function **does not** check for NaN or infinity. If the input
130/// number is not a finite float, the printed representation will be some
131/// correctly formatted but unspecified numerical value.
132///
133/// Please check [`is_finite`] yourself before calling this function, or
134/// check [`is_nan`] and [`is_infinite`] and handle those cases yourself.
135///
136/// [`is_finite`]: https://doc.rust-lang.org/std/primitive.f32.html#method.is_finite
137/// [`is_nan`]: https://doc.rust-lang.org/std/primitive.f32.html#method.is_nan
138/// [`is_infinite`]: https://doc.rust-lang.org/std/primitive.f32.html#method.is_infinite
139///
140/// ## Safety
141///
142/// The `result` pointer argument must point to sufficiently many writable bytes
143/// to hold Ryū's representation of `f`.
144///
145/// ## Example
146///
147/// ```
148/// use std::{mem::MaybeUninit, slice, str};
149///
150/// let f = 1.234f32;
151///
152/// unsafe {
153///     let mut buffer = [MaybeUninit::<u8>::uninit(); 22];
154///     let len = ryu_js::raw::format32(f, buffer.as_mut_ptr() as *mut u8);
155///     let slice = slice::from_raw_parts(buffer.as_ptr() as *const u8, len);
156///     let print = str::from_utf8_unchecked(slice);
157///     assert_eq!(print, "1.234");
158/// }
159/// ```
160#[must_use]
161#[cfg_attr(feature = "no-panic", no_panic)]
162pub unsafe fn format32(f: f32, result: *mut u8) -> usize {
163    debug_assert!(!result.is_null());
164
165    let bits = f.to_bits();
166    let sign = ((bits >> (FLOAT_MANTISSA_BITS + FLOAT_EXPONENT_BITS)) & 1) != 0;
167    let ieee_mantissa = bits & ((1u32 << FLOAT_MANTISSA_BITS) - 1);
168    let ieee_exponent = (bits >> FLOAT_MANTISSA_BITS) & ((1u32 << FLOAT_EXPONENT_BITS) - 1);
169
170    if ieee_exponent == 0 && ieee_mantissa == 0 {
171        *result = b'0';
172        return 1;
173    }
174
175    let mut index = 0isize;
176    if sign {
177        *result = b'-';
178        index += 1;
179    }
180
181    let v = f2d(ieee_mantissa, ieee_exponent);
182
183    let length = common::decimal_length9(v.mantissa) as isize;
184    let k = v.exponent as isize;
185    let kk = length + k; // 10^(kk-1) <= v < 10^kk
186    debug_assert!(k >= -45);
187
188    if 0 <= k && kk <= 21 {
189        // 1234e7 -> 12340000000.0
190        write_mantissa(v.mantissa, result.offset(index + length));
191        for i in length..kk {
192            *result.offset(index + i) = b'0';
193        }
194        index as usize + kk as usize
195    } else if 0 < kk && kk <= 21 {
196        // 1234e-2 -> 12.34
197        write_mantissa(v.mantissa, result.offset(index + length + 1));
198        ptr::copy(result.offset(index + 1), result.offset(index), kk as usize);
199        *result.offset(index + kk) = b'.';
200        index as usize + length as usize + 1
201    } else if -6 < kk && kk <= 0 {
202        // 1234e-6 -> 0.001234
203        *result.offset(index) = b'0';
204        *result.offset(index + 1) = b'.';
205        let offset = 2 - kk;
206        for i in 2..offset {
207            *result.offset(index + i) = b'0';
208        }
209        write_mantissa(v.mantissa, result.offset(index + length + offset));
210        index as usize + length as usize + offset as usize
211    } else if length == 1 {
212        // 1e+30
213        *result.offset(index) = b'0' + v.mantissa as u8;
214        *result.offset(index + 1) = b'e';
215        index as usize + 2 + write_exponent2(kk - 1, result.offset(index + 2))
216    } else {
217        // 1234e30 -> 1.234e+33
218        write_mantissa(v.mantissa, result.offset(index + length + 1));
219        *result.offset(index) = *result.offset(index + 1);
220        *result.offset(index + 1) = b'.';
221        *result.offset(index + length + 1) = b'e';
222        index as usize
223            + length as usize
224            + 2
225            + write_exponent2(kk - 1, result.offset(index + length + 2))
226    }
227}
ryu_js/pretty/mod.rs

ryu_js/pretty/
mod.rs
